The development of the manufacture of microelectronic components implies measurement and control processes and devices which are more and more performing.
Indeed the permanent reduction in the critical dimension of these circuits (CD: Critical Dimension) which is currently 100 nm approx. implies corresponding adaptation of the measurement methods. Simultaneously the increase in size of the wafers and the costs represented by each of them imply the control and the detection of the defects, as soon as possible and, in fact, at each step of the manufacturing process.
To this end, the fact that these wafers carry patterns which are repeated identically is used. The regular repeat of a pattern on a planar support brings about the realisation of an object behaving, from an optical viewpoint, as a grid. The dashes of the grid consist of the sequenced repeat of the pattern.
It is thus that, until now the inventors of this application have used, in laboratory, the Mueller ellipsometry in different spectral domains, for characterising diffraction grids.
More conventionally, the spectroscopic ellipsometry is used in the industry (often under the name “scatterometry”) for characterising the circuits. Spectroscopic ellipsometry measurements are then conducted at zero order, that is to say that the beams, respectively, excitation and measurement beams are oriented, relative to the measured object, according to angles bound by the Descartes laws, wherein the plane of incidence is perpendicular to the dashes of the grid formed of the repeat of the pattern.